This invention relates to apparatus and methods for occluding a body lumen. More particularly, the present invention provides a puncture resistant occlusion balloon, suitable for use, for example, during transluminal stenting of the carotid arteries.
Carotid artery stenoses typically manifest in the common carotid artery, internal carotid artery or external carotid artery as a pathologic narrowing of the vascular wall, for example, caused by the deposition of plaque, that inhibits normal blood flow. Endarterectomy, an open surgical procedure, traditionally has been used to treat such stenosis of the carotid artery.
In view of the trauma and long recuperation times generally associated with open surgical procedures, considerable interest has arisen in the endovascular treatment of carotid artery stenosis. In particular, widespread interest has arisen in transforming interventional techniques developed for treating coronary artery disease, such as stenting, for use in the carotid arteries. Such endovascular treatments, however, are especially prone to the formation of emboli.
Such emboli may be created, for example, when an interventional instrument, such as a guide wire or angioplasty balloon, is forcefully passed into or through the stenosis, as well as after dilatation and deflation of the angioplasty or stent deployment balloon. Because such instruments are advanced into the carotid artery in the same direction as blood flow, emboli generated by the procedure are carried directly into the brain by antegrade blood flow.
Stroke rates after carotid artery stenting have varied widely in different clinical series, from as low as 4.4% to as high as 30%. One review of carotid artery stenting including data from twenty-four major interventional centers in Europe, North America, South America, and Asia had a combined initial failure and combined mortality/stroke rate of more than 7%. Cognitive studies and reports of intellectual changes after carotid artery stenting indicate that embolization is a common event causing subclinical cerebral damage.
Several previously known apparatus and methods attempt to remove emboli formed during endovascular procedures by occluding blood flow and trapping or suctioning the emboli out of the vessel of interest. These previously known systems, however, provide less than optimal solutions to the problems of effectively removing emboli generated during stenting. The elements used to occlude blood flow may, for example, dangerously interact with a stent.
Chapter 46 of Interventional Neuroradiology: Strategies and Practical Techniques (J. J. Connors and J. Wojak, 1999), published by Saunders of Philadelphia, Pa., describes use of a coaxial balloon angioplasty system for patients having proximal internal carotid artery (xe2x80x9cICAxe2x80x9d) stenoses. In particular, a small, deflated occlusion balloon on a wire is introduced into the origin of the external carotid artery (xe2x80x9cECAxe2x80x9d), and a guide catheter with a deflated occlusion balloon is positioned in the common carotid artery (xe2x80x9cCCAxe2x80x9d) just proximal to the origin of the ECA. A dilation catheter is advanced through a lumen of the guide catheter and dilated to disrupt the stenosis. Before deflation of the dilation catheter, the occlusion balloons on the guide catheter and in the ECA are inflated to block antegrade blood flow to the brain. The dilation balloon then is deflated, the dilation catheter is removed, and blood is aspirated from the ICA to remove emboli.
EP Publication No. 0 427 429 describes a similar device with a first balloon for occluding a patient""s CCA, and a second balloon for occluding the patient""s ECA prior to crossing a lesion in the ICA.
A drawback of both the device in EP Publication No. 0 427 429 and the Interventional Neuroradiology device is that, if either is used to place a stent in the ICA, the stent may extend beyond the bifurcation between the ECA and the ICA. The occlusion balloon placed by guide wire in the ECA may then snag the stent during retrieval, causing the balloon to puncture or get caught within the artery, and requiring emergency surgery to remove the balloon.
In view of drawbacks associated with previously known systems, it would be desirable to provide methods and apparatus for removing emboli from within the carotid arteries during carotid stenting that simultaneously reduce the risk of emboli being carried into the cerebral vasculature while preventing dangerous interaction between the apparatus and the stent.
In view of the foregoing, it is an object of the present invention to provide methods and apparatus for removing emboli from within branched arteries during stenting that simultaneously reduce the risk of emboli being carried into the patient""s vasculature, e.g., cerebral vasculature, while preventing dangerous interaction between the apparatus and the stent.
The foregoing objects of the present invention are accomplished by providing interventional apparatus for occluding flow in a branch artery, the apparatus being resistant to puncture. The apparatus preferably is employed in conjunction with an arterial catheter, a venous return catheter, and, optionally, a blood filter or flow control valve disposed between the arterial and venous return catheters. The arterial catheter has proximal and distal ends, an aspiration lumen extending therebetween, an occlusion element disposed on the distal end, and a hemostatic port and blood outlet port disposed on the proximal end that communicate with the aspiration lumen. The aspiration lumen is sized so that an interventional instrument, e.g., a stent delivery system, may be readily advanced therethrough to the site of a stenosis in either the ECA (proximal to the balloon) or the ICA.
The arterial catheter illustratively is disposed in the CCA proximal of the ICA/ECA bifurcation, the branch artery occlusion device is disposed in the ECA to occlude flow reversal from the ECA to the ICA, and the blood outlet port of the arterial catheter is coupled to the venous return catheter, with or without the blood filter disposed therebetween. Higher arterial than venous pressure, especially during diastole, permits low-rate flow reversal in the ICA during an interventional procedure (other than when a dilatation balloon is inflated) to flush blood containing emboli from the vessel. The blood may be filtered and reperfused into the body through the venous return catheter.
In accordance with the principles of the present invention, the branch artery occlusion device is puncture resistant, so as to prevent dangerous interaction between the balloon and a stent during retrieval. In a first embodiment, the device includes a wedge configured to deflect the balloon away from contacting a portion of the stent extending past the ECA/ICA bifurcation during balloon retrieval. In a second embodiment, the device comprises a balloon that retracts into a capsule prior to retrieval of the balloon from the ECA. In a third embodiment, a sheath is advanced over the balloon prior to retrieval from the ECA.
Methods of using the apparatus of the present invention also are provided.